renice — Change priority of running processes

Linux / Service and process management / renice.html

Changes the nice value of processes that are already running.

Basic Information

What is this command?

Unlike nice, renice changes processes that are already running instead of starting new ones.

Targets can be a PID, a user or a process group, so a sudden heavy job can be lowered immediately.

What problems does it solve?

• Lower a job that suddenly monopolizes the CPU.
• Restore priority after a backup finishes.
• Adjust every process of one user.
• Defer low-urgency work during an incident.

Key features

By PID

Give a value with -n and a PID to change one process.

• When to use: When only one job should be lowered
• What you get: Priority applied immediately
• Limitations: A new PID needs a new call

By user

The -u option adjusts every process of a user.

• When to use: When one user loads the machine
• What you get: All processes of that user adjusted
• Limitations: The blast radius is wide

By process group

The -g option applies to a whole process group.

• When to use: When lowering a pipeline together
• What you get: Priority of the group changed
• Limitations: The group ID must be known first

Installation and usage

Check whether it is installed

renice --version

apt install util-linux # usually already present

Real-world examples

Lower one PID

Raise the nice value of PID 1234 to 15.

# Lower the priority of PID 1234
renice -n 15 -p 1234

Adjust a user

Lower every process of user deploy.

# Lower all processes owned by deploy
renice -n 10 -u deploy

Raise priority

Lower the value to raise priority.

# Raise the priority (needs privilege)
renice -n -5 -p 1234